The invention relates to an apparatus for opening a plurality of fiber bales, particularly bales of cotton or chemical fibers or the like. The apparatus (bale opener) is of the type which has a rapidly rotating detaching (opening) device arranged for travel above a series of stationarily supported fiber bales. The pins or teeth of the rotary detachers (opening rollers) project through the grate bars of at least one grate and hurl the detached fiber tufts away from the bale surface.
In a known opening device of the above-outlined type an opening roller cooperating with a grate is provided wherein an imaginary contour line touching the tips of transversely (axially) consecutive teeth and an imaginary contour line tangential to the underface of transversely consecutive grate bars are linear and extend parallel to the axis of the opening roller. The grate bars are biased against the bale face with spring forces of identical magnitude. In such an arrangement in the lateral bale zones there is generated a higher working pressure (higher force) than in the mid-zone of the bale. In the lateral zone of the bale the fiber material may escape more easily in the lateral direction so that the bars press the fiber material in those lateral zones farther down than in the mid-zone of the bale. As a result of this phenomenon, the teeth of the opening roller--whether such teeth are directly attached to the cylindrical roller surface or whether they are part of toothed discs--penetrate only insufficiently--if at all--into the bale surface and thus detach fiber tufts only to a small degree. This results in a non-uniform opening (tuft removal) of the bale surface. It is a further disadvantage that the laterally extruded fiber material falls to the floor.